Review PalmOne's Treo 600 was an impressive smart phone but, for me at least, failed in two important respects: it didn't have Bluetooth, and PalmOne hadn't quite managed to abolish the stylus. Yes, Graffiti was gone, but you still needed to reach for the pointer, particularly if you were coming to the machine as a PDA user.

The Treo 650, recently released in the UK at long last though more than six months old in the US, addresses both problems. It provides a number of other tweaks too, making it more a refresh than a major new release.

PalmOne would probably prefer reviews highlight the 650's higher resolution, 320 x 320 display, and it's unquestionably an improvement over the previous model's 160 x 160 job. The new screen really does make it worthwhile keeping photos on the phone, and even makes the most of those taken on the handset's own camera, still set to 640 x 480 but with enhanced light sensitivity to make it more suitable for indoor shots.

For me, the Treo 600's screen wasn't a deal breaker. The new screen is the same size as its predecessor, and its what that mean for the handset's own dimensions that was the problem. PalmOne did what it could to keep the 600 small but the square screen means it wasn't as comfortable to hold up to your ear as a typical candy bar mobile phone. The 650 is roughly the same size as the 600, but with Bluetooth on board, it can stay in your pocket while you speak through a wireless headset.

Well, almost. The 650 is less headset friendly than my 18-month-old Nokia 6600. Pairing is a doddle - the 650 got talking to my Motorola HS850 just fine - but the phone doesn't maintain the connection, presumably to save power. Get a call and the headset isn't activated automatically as it is with the Nokia, leaving a short but pregnant pause while you press the button to link the two devices up - and your caller wonders if they've got through to you.

I also felt this sense of being not quite right with the 600's user interface. You could never quite run it exclusively from the five-way navigator control - every so often you needed to reach for the stylus. With the 650, PalmOne has extended the work it did on the Palm OS - 5.4.5 in this case - to make it entirely button-operable, but it's not all the way there yet. You still can't switch between day, week and month views in Calendar without the stylus, for example, but overall there's a much greater sense of independence from the touch-sensitive screen. You can use the 650 one-handed.

PalmOne has shrunk the navigator's control and app-select buttons slightly but not so you'd notice. The addition of call make and break buttons is a bonus and makes the 650 feel more like a phone. The shallowly curved keyboard is better, but it's not a big improvement over the previous one. Nor is the slightly more compact antenna stub. Europeans hate it, but North Americans love it - it speaks volumes about the handset's ability to pick up weak base-station signals, apparently - and that's why it's there. Me, I'm not bothered, though the new version is less intrusive.

Other improvements include a removable battery, and using Flash for main memory. Yanking out the battery, putting it back in and finding all your information's still there is a real thrill. No more backups - unless you want to cover yourself against the need to perform a hard reset of course. I didn't need to, but my evaluation unit did crash once during the weekend I spent with it.

Back to the battery, and its capacity is good. I only noticed significant charge loss when typing this review - and that's because the backlight was on. The rest of the time I had Bluetooth on permanently. With Bluetooth headset usage, rampant texting and quite a few voice calls, not to mention an hour or so writing this, my 650 went from a full charge down to under 20 per cent in just over three days - better than almost all the other smart phones I've tried.